Supersubstorms during strong magnetic storm on 7 September 2017

Abstract

We analyzed the appearance of two supersubstorms observed during storm on September 07, 2017. Supersubstorms (SSS) are called substorms with SML index < - 2500 nT. The storm on September 07, 2017 is famous event which was studied already in many papers. There were two several geomagnetic storms on 7 and 8 September 2017, which associated with two consecutive solar wind structures: SHEATH with EJECTA and SHEATH with magnetic cloud (MC). Because the first SHEATH have a positive IMF Bz on their front edge the substorm activity absent in this time. The main phase of the first magnetic storm began with arriving the second SHEATH with the strong negative IMF Bz. During this period the first night-side supersubstorm (up to ~ 3500 nT) developed. The second magnetic storm was caused by MC with the negative IMF Bz and the severe night-side supersubstorm (up to ~ 3500 nT) were registered in this time. Thus, during the 7-8 September 2017 storms, two supersubstorms were generated, these supersubstorms caused by the SHEATH and MC impact have demonstrated the global scale distribution.